yeah the matching of t-pieces and hose is the tricky bit.. From memory the T-piece i got with my autometer gauge was WAY to big for the stock hose..
So i actually went down the path of getting a custom copper T-piece from a hose supply place in 2.5/3mm i think (closest to stock). you will struggle to find anything aftermarket in the same size as the stock hose.
Then i bought the new hose in the size to match (then again cant really get hose thinner than 2.5mm).
If you increase the size of t-pieces and hoses slightly, dont stress too much.. All you will lose is a few ms of response time from the gauge but the reading should remain accurate as long as there are no leaks. If you want to get really technical and keep the same response time with a fatter hose, just make the hose shorter, as its the internal volume that makes this difference..
R33 may have a larger hose from stock tho, which would be helpful and much less stuffing around..
hope that makes sense..