Try Icom America Parts in Washington state.
I bought one from Icom parts around a year ago. They had pretty many heads in stock at that time I was told when I ordered mine.
It was very reasonable at that! You should be able to Google and find Icom Americas phone number.
I'd imagine the 2500 you bought was probably the PCR2500 which was sold without a control head for computer control only. Some owners never knew there were two versions of the 2500 receiver.
A complete R2500 came with the control head which was almost the only difference between the R2500 and the PCR2500. The other differences between the two were the cables needed for the control head and another user manual for the control head itself were included in the R2500 box.