I don't know of a rye grass supplier but if your doing it for winter grazing or hay I have a suggestion. I was talking with my local Ag store owner and he said he was having the same issue you are and that it is going to be expensive this year. This all started when I asked if about getting grain rye to plant as I double crop with crab grass and rye and they are overlapping to much due to the rye grass coming back after I cut it for hay. I wanted something like wheat that stays down after I cut it so that the crabgrass can come on without competition. He stated that barley was going to be reasonable this year and what he was looking at getting due to price and availability of rye grass. I asked about tonnage and grazing which are supposed to be pretty close to equal that of rye grass and the protein is higher than that of wheat or rye grain, at least that is what I was told. I haven't read studies myself so you may want to look at some before deciding but that is what it looks like I'm going to do.
Best of Luck,
OldCrow