I have an el-cheapo I picked up for like $2 someplace. The handle sticks out the hole in the side of the grill that they usually leave for the optional rotisserie. Awesome for veggies.
What I really miss is a grill wok-ish thing- a square bent-up pan that had no handles, just a nice cooking surface for veggies and shrimps and little itty bitsies.
Ah- a nice Portabello.... hmmm.