Hi Smytrous,
I’m guessing you mean their mattress topper (vs their mattress cover) but there is no reason that any topper would only be useable on a specific mattress. Using a different mattress under the same topper will change how well the mattress/topper combination feels and performs and how well it works for you in terms of PPP (Posture and aligment, Pressure relief, and Personal preferences) so with a different mattress the combination may be a better match for your body type or sleeping positions or it may not work as well.
There is more about the different ways that one mattress can “match” another one in post #9 here but it’s unlikely that a manufacturer would be either willing or able to try and “reverse engineer” another mattress and then source and purchase the same components (if they are available to them) and make the same mattress for you. It would be a much more effective approach to try and “match” your specific needs and preferences with another mattress rather than trying to “match” another mattress.
If you prefer a mattress that uses a combination of pocket coils (and/or microcoils) and latex there are some latex/innerspring hybrids in post #2 here that may be worth considering if any of them are available in your area. Many of these can also be customized in different ways and are also available online.
If you let me know your city or zip code then I’d also be happy to let you know about any of the better options or possibilities I’m aware of in your area that you could use as starting point to see if there are any similar mattresses available locally as well.
Phoenix