Welcome to TBN! You've come to the right place for answers. I'll try to give you a few and maybe someone else will also fill in more details. I'm far from an expert, but I do know a bit about your tractor.
You need to decide if you want a New Holland loader or if an aftermarket loader would do the job. There are many aftermarket loaders that are good choices if you have a dealer for them in your area. The New Holland will give you the best resale value and allow you to have a single source for parts that's the same as your tractor. I think you'll also find the location of the NH joystick is very convenient on the right side console instead of mounted on the loader post.
There are two New Holland loaders that have been used on the TC55DA. The first loader was the 18LA. More recently, NH has changed loader manufacturers and the new loader is the 270TL. Both loaders look very similar. I believe you will likely find the 270TL is the only available loader.
Tractors with loaders are most often built as "loader ready" tractors at the factory. That means the joystick, hydraulics, and loader mounting posts with subframe bracing are installed on the tractor at the factory. Because your tractor was not made this way, it will have to have the items installed by your dealer. That makes the loader purchase seem more expensive when compared to the loader being purchased for a "loader ready" tractor. While you will find the dealer's service department is very experienced at installing loaders, the extra parts and labor do add up to a higher price. I would expect a 270TL loader to be a little over $6000 by the time you get it installed. Full MSRP would be around $6500 with the quick attach plate and 72" bucket installed. If you don't want the quick attach option, you can save $400 to $500, but I wouldn't suggest spending that much money and getting a pin-on bucket. Quick attach is worth every penny you pay for it in my opinion.
I'd say to get an actual quote from your NH dealer and then ask him if he has other loader options. My NH dealer also sold Bush Hog loaders which were a little less than the NH. One of the posters here sells Westendorf loaders and those seem to be also a good buy.
Good luck with your tractor and researching the loader. At least 80% of the jobs I do with my tractor include using the loader. In my opinion, it is worth the money.