Bosch PDA 100 sander?

I used the sander, for some time, WITHOUT the sanding sheet in place.The result is that I have worn smooth the Velcro like surface on the vibrating head, about 50% so the sanding sheet is not secure,
Can I obtain a replacement head assembly, can I fit it myself or is it a case of buy a new sander.
Any positive advice would be appreciated --- even from B& Q offering me huge discounts on a new sander !