Canford seem to have discontinued them. They were 97 quid each (!). I found mine on ebay. At a pinch you might be able to get a VHS splicing block, but the metal ones are far, far superior if you can get one.
The tape center splicer is an aluminium VHS splicer and its so much cheaper than the markartek splicer. Can the VHS one work just as well? cos for $33 it seems like a bargain!