Are there any 8-speed brifters with internal cabling?
The new Claris, called R2000, has internally routed brake and shifter cables, an improvement on a previous version, that still sported the externally routed shifting cables.
It is still 8 speed group, so in line with the op's wishes.

https://bike.shimano.com/en-EU/product/component/claris-r2000.html



dealers manual, page 13, how to install shifter cable:
http://si.shimano.com/pdfs/dm/DM-RBSL001-03-ENG.pdf