Is there spare parts for Guitar Hero?

Yes you can get all kinds of replacement parts at www.guiatrherorepair.com

They have a parts shop here http://www.guitarherorepair.com/gh-parts-store

..and I found this one for the rock gods in the Southern Hemisphere:)

http://www.oztion.com.au/buy/auctions.aspx?type5=gtrhero

and I think you can request parts you need and they will source it.