Hi Codude.
Welcome to our Mattress Forum. 
Thanks for joining us all the way from reddit! I’ve seen some pretty interesting mattress conversations in the mattress feed over there. Long time lurker
To take some words from Phoenix…
While you usually won’t find an mattress that is “equivalent” to a “target” mattress you have tested locally made by a different manufacturer… in some cases the “art and science” of approximating a mattress has already been done to a large extent and an online manufacturer or retailer may have already “matched” their mattresses to a specific mattress. In other cases they may be aware that one of their mattresses is a close approximation to another mattress based on their own personal experience (even if it isn’t in the mattress description) so if the mattress it approximates is available locally then this would give you a chance to test a specific local mattress that was a reasonably close approximation to a mattress you are considering online. Attempting to find something that is exactly the same would be an exercise in futility and often a frustrating experience especially if you are trying to do that on your own. There is more information in post #9 here about the different ways that one mattress can “match” or “approximate” another one. This being said you could be put on the right track by seeking guidance from an experienced manufacturer or retailer (like those in our Trusted Members, who would be much more qualified to best approximate a mattress feel based on all the specs and the personal needs and preferences you may provide.
You may also find this forum topic by a DIYer who was trying to replicate an iSeries 3000 interesting, especially as it pertains to combo/specs that mimic your preferences.
I hope this gives you a useful launching point. Please do come back if and when more questions arise!
NikkiTMU