I would just use a requester (yellow) chest and set it to either

1. Fetch a little bit, less than I'm using so it doesn't hog my stockpile during transition to all-reds

2. Fetch all of it and then treat it as singular place that I get yellowbelts from instead of where yellows are produced.

Both of these approached are yellow-to-red transition friendly but the latter assumes you're getting the belts by hand and not having them delivered to you by bots. You can jank rig the latter option to also serve yellow belts by putting a passive provider next to it and dumping yellows into that. Then once you're only using reds, just turn the inserter around so it feeds your yellow stockpile back into the system or just replace the chest with a provider so the bots move them.