There are several places to order weights from, the couple that I looked at didn't list the 4815 but it all depends on the bolt holes in your wheels;
Branson Wheel Weights Suitcase Weights and Brackets
This one shows how to measure for the weights;
Wheel Weights | Taylor Foundry Company | Tractor Wheel Weights
What I put on my 8050;
Product Details - Lonestar Weights
Most places sell these weights in 1000# lots for the "free" shipping to a commercial location,
and you are looking at a bit over $1.00 per pound.
They are not inexpensive but I much prefer iron over liquid ballast, I'm running 1200# and ocassionally I'd like another 600#s.