Miter slot guide bar.
The making of a miter slot guide bar that slides accurately and is adjustable to slot width kind of becomes a bit of trial and error and may work today, but not tomorrow.
I've made a few and find that my design works out the best for me and my use.
I take a piece of wood about 3/8" to 1/2" thick and as long as I need the slide bar that I need for my application. If the piece of cut wood bows, it's not a problem. I usually make my slider about 1/32 to 1/16 of an inch narrower than the slide slot. It doesn't have to be as straight as an arrow. We'll make it fit using my design.
I drill a series of holes in the side that go all the way through. Maybe 2, 3 or even 4 depending upon the length you need. Probably 2 - 3 - 4 inches between the holes, but you want one at each end of the piece and drill those holes about 1" from the end. The size of the hole depends upon the nylon set screws that you purchase. You can get metric set screws and or sae set screws on ebay M4, M5 or M6 about 8mm in length cost $4-$6 for a box of 50. You need to make sure that you have a tap that is able to match the set. SAE #8-32 or #10-24 or 1/4" could also be used. It all depends upon what you are able to find at a good price.
I put the tap in my drill and run it in and then reverse the drill and bring it back. I do this 3 or 4 times and the last one I drill it in and then take the tap out of the drill. Don't run the last one out with the drill or hand unscrewing. You want the internal wood fibers bending to the out end. (Take my word for this because you may find that you can't take the set screw out by backing it out.) To get it out you drive it all the way thru and then start it again. On set screws that use a allen wrench I've stripped the allen socket on the set screw. If the set screw is locked in place then drill a new hole and start again a little space away from the blocked one.
Start feeding your miter slider into the table top and set the set screw so the slider moves but moves snug. Then slide it to the second hole. Do the putting in the set screw again and getting it tight but sliding.
If you have a slightly bent miter slider you will find that you are getting it straightened as you put in the set screws. I always try to put the wooden side next to the saw blade. That way the adjustment from the jig to the saw blade doesn't change if you adjust the set screw and it moves the slider away from the blade. Maybe ever so slow but it is movement.
The nylon set screws will not scrape any of your steel table saw top off like steel set screws would. If they are a little tight then some sand paper should shorten them up a little without having to reset them. Once sanded then re-adjust it to your slot.
A little wax on the wooden side will make it like "Greased Lightning". (That was a term my boss used when he wanted some new replacement software to go into a computer system. That became our motto. I made a lightning bolt out of Osage Orange (Yellow) with a black streak running through. That model saw on his desk for years.)