Those brand new Microstar or AgriStar balers are pricey at $15K plus new, but will work on really small tractors - tractors even smaller than yours.
Here are some cheaper baler alternatives in the vintage line, but best to be mechanically inclined to keep them operational as most will be 35 plus years old. In general New Holland and John Deere are the preferred brands and the most popular which equates to best parts/technical support:
a) New Holland 65 compact baler. The smallest of the vintage balers. It is my preferred choice as parts are readily available. It has a 12"x16" plunger so it takes less hp to run it. Also, The smaller plunger will shake a tractor less than a larger plunger will. Can often be purchased cheap too. There was one for $400 on Minnesota's Craiglist that looked decent -wished it had been closer to me. (I use one of these with my 26 hp Kubota compact tractor and my tractor handles it well).
b) Ford 520. Also has the small 12"x 16" plunger, but parts will be really hard to find.
c) John Deere 14T or 24T (14" x 18" plunger size which is the common standard size). The 14 T owners manual specifies a JD 40 tractor or equivalent. A JD 40 is a pretty small low hp tractor.
d) New Holland. Any model numbers between 67-273 (will have the 14" x 18" standard plunger size). Skip the 66 (the 66 is small and kinda neat but has lots of wood in it. They can work well though) and definitely skip the 77 (the 77 is huge, heavy, and kinda crude - it also has a 16" x 18" plunger so it would not be a good choice).
e) Some of the Massey's are also good balers (10,12, 124)just not as popular as NH or JD so a little less support in parts, but more importantly, less technical help from past users (i.e. fewer pool of experienced MF baler experts for newbies to ask technical questions and seek advice from).
f) There may be some newer balers that will work too, but generally speaking the newer balers were designed for more capacity (i.e. faster baling) so they will need more hp to run. Most owner's claim they need 40 hp to 60 hp to work well with the smallest of the newer balers with the 14" x 18" plunger. I would skip any baler from any vintage with the larger 16"x 18" plunger size. When the lower capacity vintage balers listed above were made the majority of the tractors were only 20 to 40 hp so they were designed to work with lower hp tractors common to the era.
Do some searching at his site (and yt tractor) as this topic has been covered extensively. You will find both success and horror stories. In my opinion the horror stories stem from people not making wise choices with the baler choice based on their tractors known limitations. (e.g. Think of it kinda like pulling a travel trailer with a full size 1/2 ton truck with a small V6 engine. The little truck can do it rather well if you pick the proper travel trailer size/weight to put behind the truck. Knowing your terrain/travel path can further help your success if you account for it. If towing in the hills better to go with an even smaller trailer choice to have some power reserve. Pick a huge/heavy trailer that should be behind a big 3/4 ton V8 diesel and the towing experience will be a disaster with your small truck - similar principles apply when matching your baler to your tractor).
Lastly, remember you can always drop the bales on the ground in lieu of trying to pull a wagon behind the baler. Depending on how light your tractor is it may be best to do this especially if you are on hilly terrain. I drop on the ground because I do not have a wagon and can not justify buying one for my small operation. I simply pick them up later with a pickup truck and flat bed trailer. I prefer this as it keeps me out of the dust and I can do everything as a one man operation if need be. Actually, I usually have the wife run the tractor and baler while I load the trailer using the pickup truck. If anything breaks I transition to fixing the baler (40 yr old machinery can be contankerous sometimes-LOL) while she transitions to loading the trailer until I get the problem fixed. Another benefit to the compact balers like mine is that most women can handle/load the bales easier due to the slighty smaller size bale. A trailer is also easier to back into the barn as compared to a wagon.
