Not easy to do as it depends on what you expect of the PSU.
if you want an HT supply for a tube circuit than a tube supply is pretty much comparable to a solid state. You might say the solid state was is more efficient but that's not generally an important parameter and you might say the tube one has a built is slow HT rise which might possibly be an advantage (though many would argue it is not) but you can replicate that in a semiconductor supply with ease.
If you want a dc supply for heaters then it's quite easy to build a semiconductor regulator but you'll probably need a chunky heat sink and there's really no practical way to realise this with tubes.
Cheers
Ian