odds are there are more of that used tractor sitting around somewhere, locating it is the issue. So, lets see what our members here have as far as locating or assisting in regards to this part need.
Many tractors that didn't meet the EPA still were imported into the States for years after. Through various loopholes etc.. so don't assume you got the only one!
This may be a stretch but I would try to find dealers in Europe, Australia, New Zealand and Asian countries. These areas never had to deal with EPA regulations so would have a better chance of having non EPA tractor parts.
I'm working on a possible solution,are you 100 percent sure of the actual measurement ? I checked a older 204 tractor with a TY290 and it was the same as the 254