Put it on ice?

You mean the one which holds the engine steady, don't you! Happened to
me to, and fixing it is an engine-out job. I fabricated my own
replacement which uses the remaining steady bolt and one of the clutch
housing bolts, which has done the trick (though I do intend to put it
back to original when the engine next has to come out). Plus I'm going
to add a bottom steady; I have the bracket which fits the gearbox, but
no mounting on the subframe at present. And my engine is a bit vicious
;-)

I believe Minispares, among others, do a similar proprietary bracket,
though I've heard people say they're not that good. However it is, like
mine, a reasonable short-to-medium term fix.

I don't know anything about the Ultimate Engine Stabiliser, but I'd be
very wary of using the thermostat housing for that job. Apart from the
fact that those studs are themselves prone to breakage if not treated
with respect, the original engine steady is attached to the block, while
the stat is on the cylinder head. So ultimately you'd be putting more
stress on the head bolts.