You need a 10-speed chain.
Difference is in width and other stuff.
Any 10-speed chain will do.
https://www.ebay.co.uk/itm/KMC-Z51-...-Road-1-2-x-3-32/351343640318?redirect=mobile
Loads available, I have an old rivoli chain tool to sort out the links.....
Actually, that might not work on a 5-speed block.
Actually, that might not work on a 5-speed block.