I came up with a vacuum system for my 15' Intex donut back in the stone ages--about 7 years ago.

I bought 18' of 1 1/4" hose. I found a 3/4" (ID) double-female PVC adapter at H/D. I forced the adapter in the hose, and the other end fit perfectly in the Intex return.

For a vacuum head I used a Biogard garden hose-type vacuum (like a Black Magic) that had an adapter to use as a regular vacuum head and had a 1 1/4" fitting.

While the suction wasn't the greatest, it DID catch the super-fine stuff in the filter.