Well, what to do? As has been suggested, the very best fix is replacement with a solid, good, known float bowl. However, as far as I can see, that is not a purchasable part number. You want a new float bowl, you buy entire carburetor. You buy second-hand carburetor from eBay, you can't be sure if what you get isn't as bad as what you've got.
Solder it up? Next best thing probably. Unfortunately yours truly is not that good at that (it's been awhile....).
I thought perhaps I could get some slightly oversize tubing and slide it down over the existing tube down to the alloy bowl, using a bit of Loctite or JB Weld (which someone here I think suggested??) to adhere it is place.
But then I conferred with the local shop, man named Jim Hale (props here and now to him), who provided me with what I thought is a viable solution. And that is to slide a slightly smaller brass tube up inside the overflow tube. I measured the tube ID and OD with calipers, and as it works out 3/32" is a VERY SNUG fit up inside the overflow tube. It also, at least on mine, seemed to be almost exactly the same ID as the hole at the top of the overflow tube, so I don't believe I am restricting the circuit, should it be needed.
My local hobby shop closed down, so I got these items online, a small tubing cutter and 3 pieces of 3/32" tubing. Again, pics attached.