I'm sorry, I only know of once source in the city and you must have a business license to purchase from them and they have minimum orders (of a lot of money) -GrowSouth. You can call and ask if they will make an exception for you, perhaps if you pick up. But they will ask you to order the case, everything goes by case or full flat etc. from them.

The major big-box hardware stores (Lowes, Home Depot and sometimes Ace) have seed starting flats or "seed greenhouses", they aren't as high-quantity as the ones you've got linked there, but they come with a bottom and a top cover (clear) and usually run about 72 cells total. I linked a version below. Ferry Morse makes them, as do a coupel other well known companies. Just get your seed starter mix, pour it off into the cells, add water, add your seeds. Works well. Not extremely space-effective (would be better if it were 144 cells), but it works and it's cheap, and recylcable.

Here is a link that might be useful: Jiffy Seed Starter Greenhouse

I almost forgot to add WHERE you will find them in the store. If you head towards the seed rack area in the garden section, the greenhouses AND seed starter mix are normally there. IF not, ask any sales associate about "Seed greenhouses" and they should know what you're talking ab out.

I've also seen these at WalMart over here on Gresham, so I must assume that they're at other WalMarts as well, inside the store, near the garden section entrance, close to where they keep the exterior decorations like holidays lights, lawn stuff, etc.

Last year I got some of those 8-pack flats from some landscaping crew, for free. They are much sturdier than
big box store things and of course ARE free. Some have 4" pots
Those are really sturdy.
I will do the same next year too, GET FREE FLATS AND SAVE THEM