need something smaller/ lighter than a MacLaren Techno

I'm thinking of buying a super cheap lightweight umbrella stroller and could use some advice.

I already own two strollers (Maclaren Techno XT and BOB Revolution) which I hardly ever use anymore because my son (21 months old) enjoys walking a lot. He doesn't mind being in the stroller, but I like to let him run around and tire himself out (especially when we're at places safe from cars, like the zoo or a park) and really only end up using the stroller after he exhausts himself and needs to nap.

My car broke a few months ago and I decided not to replace it right now because I live in the city and can get around fine without one. However, I've realized that both of these strollers (even the Maclaren) are too much of a pain for me to want to take them with me on the bus and are also a pain to bring to the zoo/park because it's difficult to schlep the empty stroller and hold my walking toddler's hand at the same time.

My ideal stroller would be absolutely no frills, super lightweight, and fold up small enough that I could attach it to a camping backpack and walk around hands free. Does such a thing exist? I don't really care about the frills like recline, storage baskets, etc and am thinking that maybe I need to be looking at a super cheap stroller like this $17 Cosco Stroller to meet my needs. Am I crazy to think that I'd be better off with a cheapo generic umbrella stroller rather than my top of the line MacLaren which I never use?

I really don't think you'd be happy pushing a Cosco after a BOB & a Techno. I'd sell the Techno & look at getting either a Uppababy G-lite or Maclaren Volo if you want good quality as well as super lightweight. Both are ~8 lbs., so they're only 2 lbs. more than the cheapie one and about 10 lbs. lighter than the Techno. They both have carrying straps and I think will be much more comfortable for you & your son than the Cosco or similar brands.
P.S. If you ever have more stroller ?s, you will get a lot more traffic in the Baby Bargains stroller forum. :) http://windsorpeak.com/vbulletin/forumdisplay.php?f=13

or mac stark might be a good option.

I completely agree with Kaylee's advice.

But if your son is rarely in a stroller and you want something you can carry on your back, why not get a good quality toddler baby carrier (the toddler kinderpack comes to mind, although I've never owned one)? That'll be much more compact for your needs than any stroller out there. :)