does anybody have any suggestions for an online source for a straight pistol length AR15 gas tube. I have found carbine and rifle lengh, but no pistol length.

I am trying to put an adjustable gas block on a 0.875 barrel for a 300BLK build. The normal curved tubes miss the port to enter the upper by about 1.5-2mm. I can push the tube to fit into the port, but it's at the wrong angle to engage and seat into the gas key. a straight tube should run right in perfectly.

Get a straight carbine length, cut muzzle end to desired length with quality brake line cutter, insert into inexpensive gas block that has been cut in half along the axis of the barrel to use as a jig. Drill pin hole 1st, pin, then drill gas port hole. Unpin, clean any burrs.

I would do like mentioned below. trim to fit.