Fused Spur Unit Question - Is it Repairable?

Hello,
I have a fused spur unit in my kitchen for my boiler. The little white tab that covers the fuse is broken and it failed it's safety test because of this. The gas man wasn't very helpful so I was wondering if is it possible to buy a replacement tab or do I have to replace the whole unit? If I can buy a replacement tab where is the best place - I've drawn a blank on google so far! Do the tabs have a specific name? (sorry if this is a silly question: obviously I know nothing about electricals!)