IKEA's new SJOSS chargers offer all the latest fast charging protocols at a price, much lower than the competition...
Looking at the charging preferences of the Steam Deck, which from my research wants 45W at 15v/3A, it looks like the larger model should work just fine. And with it being $15 USD / $18 CAD this could be an incredible bargain.
It's so new though I can't find any info on it being used with a Steam Deck. I'll definitely be grabbing one to try, as it would be perfect for my USB hub that sits by the TV.
You can also use Chromebook chargers, as long as they support the right power spec.
I've been using one for my dock, and it's worked great. I went with the 65w ($15) to have extra power for accessories on the dock, but they also have just a 45w one ($9) that supports the Deck's 15v/3A charge.
Obviously these are more bulky than a standard charger, but it's hard to beat on price.
I would be wary of such cheap USB-PD chargers. It is not uncommon for them to fail in ways that kill devices (I work for the tech department of a school district and we unfortunately have a strict OEM-only policy around chromebook chargers due to a wave of these killing chromebooks)