Word of warning, though, it's pretty darn expensive. I think that typically striking a real film print from a digital master can be upwards of $30,000-$50,000 for a feature length film.
Keep in mind that virtually all festivals now will accept digital masters... some will only accept digital masters (even Sundance had an all-digital-required year a couple of years ago until some entrants balked and insisted on 35mm prints, so they relented the following year). So, are you absolutely sure that a 35mm print is required? Maybe not... but if so, I guess you are stuck.
I don't have any sources off hand, but there are labs in LA that do that (and one well-known one in Vancouver whose name escapes me).
Most of those labs really like to be in on the pre-production when you know a film print is needed so that you can do everything exactly right to make the right master that will yield the best print. But of course they can do it after-the-fact as well.
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