I don't know of a supply of centres as such, but what you need is a
headstock bush which converts the non-morse taper in the headstock to
3MT, into which you can pop a normal centre.
I got mine from with my 140, but they were a standard Harrison item,
and you often see them in the dealers. It'll be the same as the bush
for the L5 and L5A machines as well. It would be worth giving a
couple of the dealers a ring. Failing that, there's a company in
London who are the "official" suppliers of spares for pre-M series
Harrisons. I can't find their details at the moment, but a call to
the Harrison spares department should give you their name (that's how
I found out).
Hope this helps
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