Hi whippetmom,
This is the part that you will need to decide on for yourself since a mattress that is “exceptionally comfortable” for one person may be completely unsuitable for someone else to sleep on.
I’m assuming that you’ve read the mattress shopping tutorial here but two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your own Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists based on all the other parts of your personal value equation that are most important to you.
Many local manufacturers can make custom sizes (usually for a small upcharge). The better options or possibilities I’m aware of in the Los Angeles region (subject to making sure that any mattress you are considering meets the quality/value guidelines I linked earlier in this reply) are listed in post #2 here.
The San Diego list is in post #2 here.
I don’t know which of them make custom sizes off the top of my head so you will probably need to check their websites or call them to see which of them make the type of mattresses you would be interested in testing in the size that you need.
There are also some online options in post #2 here that may be helpful as well.
Phoenix