Most of the suitcase weights for compacts are about $1/lb. Just about any tractor place can get them for you. I had no luck in finding second hand weights in my area. If you need a lot of weight (I have used 300 lbs on the front of mine for brushhogging steep inclines), your wallet will fare much better if you come up with an improvised solution. I use 25 lb barbell weights on a 1" solid steel rod that passes through each side of the weight bracket. The original bracket is not large enough to accomplish this. I bought a weight bracket intended for a L295 and modified it so 8 of the plates will fit inside the bracket with 4 on the outside. I've heard of others who had access to metal cutting equipment and made suitcase weights from 1" plate steel, old forklift forks, etc. I've also seen guys who were handy with a welder fabricate very nice looking custom brush guards that provided adequate weight for the front end. These tractors don't have power steering, so I personally like the removable weight option. Makes it much easier to steer when the brushhog is replaced with a finish mower.
I'll also comment on the tire issue. I can see no reason why you couldn't run the 24" L245 tires & rims unless this a 4wd DT model. The tire circumference and gear ratios must be carefully matched for a 4wd. I think Firestone is the only company that offers a replacement for the 8.3x22 that is standard on your tractor, and it is the rice paddy heavy lug version.