I don't know about downloads but I have seen it being sold (used) on websites like Amazon, Half, and Ebay. And not for ridiculous prices like people sell TS2 for. I've also seen The Sims Complete Collection on Amazon for around $25.
You could check thrift stores and garage sales as well. I've seen it quite a few times at Goodwill. I actually got a few of my original TS2 discs from one.
I purchased the Complete Collection (used) from Amazon for around $25 after shipping. It was sent without a code but thankfully the first code I found via Google search worked. At least it wasn't scratched up.. Read descriptions carefully when buying used.
There may be some ussed copies of the Complete Collection floating around on eBay and the like, but there's no version of the Sims 1 still in production unfortunately.
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S3 simblr: http://simplysimming.tumblr.com/
S4 simblr: http://simlogic.tumblr.com/