I can find a 90 x 50 mini slide on Ebay UK, but it I suspect the workholding arrangement must be different.
Your link seems kaput..
If it’s any help, you don’t want to ‘stack’ attachments – a milling slide is best if it is bolted straight to the cross-slide with the least number of ‘interfaces’ possible in the path between work and cutter; if that makes sense?/ you see what I mean..