Abill,
I have the Denon 103R and works great on the RB250. Mine is OL Silver (moded 250). I know it is a little bit high from your budget stand point, but the arm needs a medium to low compliance cartridge because of the mass. Another good match when I have the RB300 is the Benz Ace series which can be bought used at around $250. Also, the regular Denon 103 is another cart you could consider and I believe is priced lower than the R version.
regards