My apologies for an imprecise answer. Some (not all) protractors are indeed designed for one specific tonearm mounting distance only.
That will probably include ANY Rega-specific protractor, which will be designed for the Rega-specified mounting distance of 222mm. I'd be surprised if there were one designed for 219.5mm.
Attaining a Rega-standard alignment with the arm at 219.5mm could be problematic. You may not be able to slide some cartridges far enough back in the slots to line it up. Whoever mounted your arm decided they wanted to use Baerwald alignment, not Rega. That's why they put the arm at 219.5mm.
Regarding protractors for your situation, I should have said, "any GENERIC Baerwald protractor will work". Some protractors are designed so that the protractor has to be precisely aimed at the tonearm's pivot point BEFORE aligning the cartridge. Any such protractor will work with your setup.
Like Lloydc, I'm a big fan of the MintLP protractor and agree that it's well worth the $110 cost (nearly all who've bought one agree). I didn't mention it because the MintLP is NOT generic. It's custom made for each table/arm combination and it's specific to the arm's designed spindle-to-pivot dimension (222mm in your case), which makes it useless for any other spindle-to-pivot dimension. Whether Yip (the maker) would be willing to build one for a Rega mounted at 219.5mm is unknown to me. You could ask him if you're interested. He might be willing to modify his design to suit. Whether you'd achieve the sonic benefits others have enjoyed is also unknown, since you're using the arm at a non-designed distance.
Note: if you use a Baerwald protractor, the cartridge will end up pointing a couple of degrees outward of square (relative to the headshell). This is because the Rega's offset angle and effective length were not designed for Baerwald. Many people prefer this setup to the Rega standard so it's not necessarily a flaw, it'll just look funny.