[physco_nutcase_danny]

You want Aluminium or better still Stainless steel..Don't fu*k about with steel.

Ebay

http://www.ebay.co.uk/itm/aluminium-tube-19mm-od-x-15mm-id-x-200-long-/330666072570?pt=UK_BOI_Metalworking_Milling_Weldin g_Metalworking_Supplies_ET&hash=item4cfd3bd9fa

http://www.ebay.co.uk/itm/18MM-OD-X-15MM-ID-316-STAINLESS-STEEL-TUBE-X-500MM-/320634097115?pt=UK_BOI_Metalworking_Milling_Weldin g_Metalworking_Supplies_ET&hash=item4aa7480ddb

Does the spacer have to be 20mm o.d????

if so,then purchase a length of 20mm o.d bar and get the i.d machined out to 15.2mm