Motorola PMLN7324AS generic option board kit DP4400e DP4800e XPR7550e DM4400e DM4600e XPR5550e etc
New, old stock, I think Motorola have now discontinued these.
This option board fits all DP4000e, DM4000e, XPR7000e, XPR5000e. It allows third party software to be run on a radio, but I'm afraid that I've never tried using them myself, so can't offer any advice.
NOTE THESE BOARDS ARE ONLY SUITABLE FOR THE "e" MODELS AND ARE NOT COMPATIBLE WITH NON "e" RADIOS
I will combine shipping costs if you buy more than one item, message me before buying or eBay will probably force you to pay postage for each.