I think I have found an inexpensive way (on the margin) to seal standard mason jars with flat canning lids.
You need a vacuum sealer and a vacuum canister that is large enough to hold the size jar you want to use.
Place a clean flat canning lid on the jar (which has been filled leaving enough head room to hold the vacuum). Place this jar in your canister and attach the vacuum lid.
(The noise may frighten your assistant.)
After it has reached a vacuum, allow the air back into the canister.
At this point the jar inside should have achieved a vacuum seal.
A gentle check with the thumb should confirm.
Note: this is not a replacement for hot water canning, but it will extend the shelf life somewhat of many items.