Some folks had that issue last summer too. I tend to buy when they go on sale after the season is over so I'm ready for the next year. Think I still have enough for this season but haven't checked so thanks for the tip to go check now. I was having my kitchen remodeled during the winter last year too so didn't think about stocking up on canning supplies for this year. At least now I have all my canning equipment in one spot excluding my jars as before they were some in the kitchen, some down in the basement and the rest out in the garage. Of course now my stove decided to jump in on the bandwagon and start acting up so may not be canning or making my winter soups this year at all.
Good luck on finding flats. Think one gal went online and ordered some but they weren't going to get here till October, way too late for canning so I gave her half of what I had.