If you need to keep something as original as can be, lead clearly has
to be replaced with lead.  But if you're just keeping something
playing, and the old lead has to come out and rubber won't stay the
right shape, what about using copper brake-line tubing?  It's not
_that_ cheap, but it's safe, easy to get, easy to handle, easy to
solder, sticks fine with burnt shellac (give it a bit of a sandpaper
in case it's coated), seems pretty strong, is attractive and doesn't
look offensively out of place.  There are a few fairly easy tricks to
get a dark patina if the copper is too visually obtrusive.

If you need larger sizes, perhaps "micro-bore" copper gas pipe; it
comes in a fair range of sizes.  In the UK all the cheap stuff will be
metric, maybe inch is more normal in the US.  You can get imperial
sizes from model engineering suppliers, but more expensively and often
thicker walled, used for the fire tubes in tiny boilers where it has to
deal with higher forces than we do.  Those guys are often masters of
tight, neat pipe bending too -- I believe mostly done with Field's
Metal.

NB: I have not used this for player instruments, yet, but I've worked
with it for other mechanisms.  So there may be an instrument reason why
not.  Nevertheless it'd be the first thing I'd try if I had lead to
replace.  There is a certain amount of copper tube in my 1910 Gotha
Steck so it definitely works -- I have no idea if that is original or
replacement.

Lester Hawksby