I occasionally suffer from the same problem where I'm forced to be stood so close to my rig that I sometimes can't hear myself at all!
As I use a pair of Orange isobaric cabs, even when they're stacked they only come up to just above my waist, so the sound will miss me completely.
The platform mentioned above would do the job and not take up much space, but would not raise the top cab high enough for me.
What I have usually found is that due to the small footprint of my cabs, there is usually a small pub table going spare that does the job admirably.
On other occasions, I've been loaned an empty beer keg or plastic beer crates (good for stacking as they lock together), both of which put my top cab at about shoulder height.
This works extremely well, at no cost to me, and no extra loading - as we tend to play the same venues regularly, the keg, table or crates are usually there waiting for me now 😎😉.
It's always worth an ask, but appreciate that these are not something to always rely on being available. As a matter of courtesy, if I'm using a pub table, I always put some beer mats under the feet of the cab to prevent scratching........