I have included a list of some of the main manufacturers currently selling thermals:
Pulsar: The Pulsar Trail XP and the Thermion XP series would give you a better image, but less native magnification and larger FOV. The Trail has a larger capacity battery than the Thermion, but doesn't have color palettes/reticles. The Thermion is also better suited to be used on bolt guns vs the Trail. Either, XP series meets your requirement.
Trijicon: Trijicon makes thermals with great clarity. However, they don't have an integrated battery. There is a Rechargeable Power Kit, so that might be an option for you but you would be at around 2.5 - 3x the investment of your APEX.
Flir PTS Series: They take CR123 batteries. I have read they do allow rechargeable CR123s. The device has to account for 3.7v power vs 3.0 for rechargeables to work. The Flir PTS scopes also have a picatinny rail on the side, so a battery pack could easily be connected and with a short 1' foot cable, it would not be in the way. This is what I run. However as of today, the PTS series is a 320x240 resolution scope. So, image wise, it wouldn't be an increase in clarity. When their 640 scopes release, it would be a step up.
Bering Optics: Bering Optics thermals such as the Hogster-R and Beast-R all take CR123s and rechargeable CR123s as well as a battery pack. However, the battery pack would be similar to what you are dealing with today and image quality would be similar to your XQ38. It is a much more compact scope so easier to use as a scanner, but still doesn't solve your exact need.
ATN: The Thor thermals have an internal battery so no wires, but you are going to have a hard time buying one from a dealer as they are mostly carried by big box stores or large online retailers due to their high return rate. You would have to move up to their 640 series to potentially have a better image than your XQ38. Due to a lack of market confidence, their resale isn't as high as many other thermals.
N-Vision: Another company with an image that would be an improvement would be N-Vision. Their scopes allow for CR123s, rechargeable CR123s, and/or a battery pack.
Something to keep in mind with an internal battery (like ATN) is if something goes wrong with the battery, the scope needs to be sent in for repair. If the scope requires a proprietary battery you better make sure it allows for an external power supply, so you aren't stuck with a brick if the scope and parts are no longer made. If it accepts external power supply and/or other types of batteries AA, CR123, etc, you always have a way of powering the scope.