I have diamond plate for skews and scrapers and a pocket sized oil stone for my parting tools.
This is the diamond plate I have been using in 1k grit,ignore the bad review (Guy probably was using the plate dry, always add water or light oil)
Axminster Premium Diamond Bench Stones - Diamond Stones - Sharpening - Hand Tools | Axminster.co.uk
This is the stone
Faithfull Combination Oilstone Aluminium Oxide 100 x 25 x 12.5mm - Oilstones - Sharpening - Hand Tools | Axminster.co.uk
Remember to keep them clean and covered when not in use (don't wipe them with tissue or keep them out while turning,dust will block up the pores)