You can quasi do bitcoin with GBTC stock. It seems to track bitcoin pretty well. Are you sure you want to do an IRA though? Hopefully you can avoid paying too much in fees.
https://goldiraguide.org/top-bitcoin-ethereum-ira-companies/

How to Add Bitcoins to Your IRA
In order to invest in Bitcoins for your retirement, you’ll need to have a self-directed IRA. Self-directed IRAs permit diversifying Roth or Traditional retirement assets beyond the usual stocks, bonds, mutual funds and certificates of deposit. They permit investors to hold real estate, tax lien certificates, promissory notes, gold and silver, private placement securities and more, as long as they can find a custodian to manage their account. Bitcoins fall into this category of nontraditional investment. https://www.rothira.com/invest-bitcoin-roth-ira

You will probably end up going with a company from this list.
https://www.innovativewealth.com/wealth-management/research/self-directed-ira-industry/the-ultimate-list-of-self-directed-ira-custodians-and-administrators/

It doesn't look like there is much transparency when it comes to fee structures. :(