There is no option without spending a lot of money.
The closest thing you can get for under $2k is a Sig 551-A1 but it's still only an American'zed version of the Sig 551 not the 550 and it doesn't even have a stamped receiver like the Swiss version does
You could theoretically buy a Sig 550 parts kit from Colorado Gun Sales and it will give you pretty much all the parts you will need to convert your Sig 551/556 rifle into almost an exact clone of the original 550 but the kit will cost you $2,700.
If you were to go the route of converting a Sig 556/551 into a 550 using the parts kit you still need to deal with keeping the gun 922r compliant which will only make your build more frustrating.
Ideally you would want to track down a Sig 556 stripped upper and 556 lower parts (hammer, trigger, sear) to give you some additional 922r compliance parts. The stripped receiver counts as the actual gun for your build and will require an FFL, between the 556 stripped upper and 556 lower parts you would have four 922r compliance parts. The barrel that comes with the 550 parts kit is US made so now you have five parts and I think you would only need one more US part after that to make the gun fully 922r compliant when the build is complete.
The good news is that the 550 parts kit has all the parts you will need in order to build a complete 550 upper using a stripped 556 upper receiver. The kit also comes with the original Swiss 550 lower and the 556 internals should work just fine in a Swiss made 550 lower. Assemble upper and lower receivers, put the two together and your end product would be as close to a genuine Sig PE90/550 that you will probably ever get without spending many thousands of dollars.
The bad news is this, good luck finding a Sig 556 stripped upper, the Sig 550 parts kits are rare and expensive and finally assembling both the lower and upper will probably be a bit labor intensive and require a bit of gunsmithing.
IMO if you want an inexpensive Sig 550 you're only real option at this point is to buy one of the new Sig 551-A1's or wait a while and perhaps Sig will give us a US made version of the Sig 550 or something close to it.