Bulkhead mount with clear sight tube & drain plug at bottom.
Bought this 2nd hand but no longer needed, tiny ding in front, can be seen in photo, the tank should polish up quite nicely though.
OBP oil catch tank
Ash breather filter
Details & measurements here:
http://www.obpltd.com/2-Litre-Square-Bulk-Head-Mount-Oil-Catch-Tank-OBPCT002?filter_name=oil%20catch
These are £52.80 + delivery from OBP.
£30 + postage at cost (I can't get to post office until Saturday)
Pick up welcome from North Herts.
Would consider swaps for a type 9 gear lever extension.