The latest MOT test advised that several joint dust covers were split.

Is it possible to source and replace these without the joints which were ok?

 

There have been multiple posts over the years detailing dust cover replacement. If I recall correctly, the covers are not sold separately by the dealer parts network, so you will have to go to places like eBay for your covers. The caveat is that not all eBay parts are created equal... You might want to run a search of the forum and see if some of the posts indicate sizes/sources for the parts.