where can i buy this spare?

What results did you get when you searched for "power devil tool spares" ? Did you see any results for Solent Tools?

Having said that, it's highly likely that the Chinese pile 'em high and sell 'em cheap, store branded tat, will have minimal support at best - probably limited to simple consumables like blades (maybe) and possibly motor brushes.

You pay more for a premier brand partly because they are much better supported.

Fghhdds
April 2020