Small factor phono stage

The EAR phonobox should fit the bill!

Gold Note PH5

Moon LP 110 v2. Unfortunately it's only $600 so it probably won't work for you

Is there a preference for which kind(s) of tube the stage uses? That would inform suggestions.

It’s not tube but the Nagra BPS is excellent and is very compact. I’ve not heard a phono stage reproduce instrument tone better than the BPS. 

Check out the Lejonklou Slipsik/Entity (mm/mc), very "tube like" sound, hard to beat for the price.

@mdrone

Ahead of a tube amplifier, try Zphono XRM. I was quite amazed by this little jewel performance. 

https://parasound.com/zphono_xrm.php

I don't know what look you are going for,  but the Tavish Designs Adiago is in your price range and a great phono stage. Good luck!

Dan

I am going to tell you. Unless you need a tube or tube hybrid I would go with Hegel V10. I have this and it does a great job. Even though it is small it has a linear power supply. The transformer is in the “wall wart” if you are ok with that you are good. There is a battery powered (rechargeable) phono stage that is under $1k. They are out of Skokie. IL. I bought my Hegel V10 at 

holmaudio.com in Woodridge, IL. 

EAR or Hagerman.

I haven't heard but maybe Luxman or Zesto.  Also EAT Glo.

Tavish Adagio is really good too, but separate power supply.

+2 for EAR

+3 for EAR

I have been using an EAR 834p.  I love it for its amazing midrange and forward sound. Tube rolling made significant changes for me.  Compared to the other phono preamps I have from Pass, LAMM, and Hagerman, it holds its own merits.   

SPL Phonos, https://hifiheaven.net/product/spl-phonos-riaa-phono-preamp-with-voltair-tech/