For all pre-2005 Ibis bikes, I recommend you find a LOCAL to you framebuilder who works in whatever material your original Ibis was made. If you’re north of the Golden Gate Bridge I would not hesitate to recommend Jeremy Sycip (707-542-6359) or Steve Potts (415-663-1974).
The map on the question below also has a ton of potential sources for builders who might be able to repair or retrofit your frame.