The CDC does not "recommend" vaccinations over 45, mostly due to previous exposure. I suspect one can find doctors willing to do the vaccination for those over 45, though one may need to convince them.

Whether this is useful depends. HPV 16 and 18 are the "high risk" strains most associated with cancer. Depending on your sexual history, getting vaccinated at 45+ may be useful. Unfortunately, there's no reliable test for HPV 16 and 18 for those who have already had it.

https://www.cdc.gov/vaccines/vpd/hpv/hcp/recommendations.htm...

The FDA approval is up to age 45, any use after 45 is off-label. Off-label prescribing is perfectly legal, but it might be difficult to find a medical provider willing to do it. You might have the best luck going to a place that specializes in sexual health (like Planned Parenthood).