I've a 1000SE too which i'm about to set up to work on my inverted T slotted Hammer K3 and F3 sliding tables.
The 3/8 X 3/4 in US standard bar on the gauge is too large for the upper vertical bar of my T slot, and narrower and thinner than the lower/horizontal bar of the T.
My plan for what it's worth is to try some UHMW tape i bought from these guys
CS Hyde to build up the sides and bottom with one layer of tape on each face for the full length of the bar. As it happens there was a size of tape available to suit my bar/slot combination exactly - and it fits all three sides.
Because it means packing the bar to fit in the lower horizontal section of the slot i've had to fit an approx 4mm spacer on a new longer pivot Allen screw between the bar and the gauge itself.
Tape is a bit of a misnomer. UHMW is a hard and highly wear resistant polymer, the 'tape' i got is around 2.5mm thick and sticks like buggery.
I tried some short pieces and it looks to work fine, the issue is perhaps that the only way to get the bar out is to slide it out the end of the slot in the 2500 long sliding table - it won't lift. It could be also that it may be inclined in practice to jam up a bit with dust as the clearance at the bottom of the slot will not be very large.
If it proves a PIA i think plan B is simply to have the mitre bar machined down to fit in the top part of the slot and zinc plate it again.
Incra have spare bars available to suit at relatively low cost, but unfortunately they offer no alternative sizes. I asked about the possibility of their supplying a metric item, but no go.
ian
PS How in heaven did we end up with so many oddball mitre slot sizes?? My Robland was even more weird, it had a shallow dovetail section slot that tended to jam if it got dust in it and the fit of the original mitre bar was truly awful.