Split queen mattresses are incredibly rare in comparison to split king beds, since split queens are a specialty size and split kings are essentially 2 twin XL mattresses sold as a single bed. PlushBeds is one of the only brands we know well enough that has some split queen offerings, as most other brands that sell this size of mattress either aren't well-known or they're a specialty/custom shop.
Unfortunately these specialty shops often charge much more for a split queen than you would pay for a typical queen, and since few people buy them it's a tossup as to whether they'll have the reviews or customer-friendly policies that most reputable mattress companies do.
Depending on your reasons for needing a split queen mattress, there may be some other options. If you're just looking for a queen with different firmnesses on each side and don't necessarily need the split, then an airbed mattress may work for you. Airbeds are designed so you can adjust the firmness on each side for sizes queen or larger (SleepNumber was one of the first big brand names for this style of bed).
If we can answer additional questions, please do not hesitate to reach out to our Sleep Solutions Team, Monday through Friday at 844-757-9355 or contact us here.