That Taiga jig is pretty nifty.
Given you use a 30mm copy ring, why not just acquire a smaller plunge bit and just wiggle it to remove the excess? Sure it would be *nice* to do it in one plunge, but to save 3 seconds at $140 seems.... silly.
Weird they don't also sell the 20mm bit.....
edit: perhaps you could use this 20mm bit
https://www.amazon.com/Freud-Double-.../dp/B000P18UNS from Freud, but obviously its no good for straight out plunging. If you pre-drill the centre of the hole with a 10mm Forster or drill bit (or such) with a hand drill, you should be right. No need to even be half accurate on the first one....
Thought 2: perhaps, like some of us, you may have a second router? Buy a small 1/2" (or so) plunge bit, plunge the centre, then use router 2 and the 20mm plunge bit? Bit of extra work, but saves spending a load on a specialised bit and/or fitting a 20mm Forster bit to the router.... (yikes!)