Yes, there are IRA custodians that will allow you create a self-directed IRA that lets you invest in almost anything that is legal for an IRA to invest in (real estate, private equity, private stock, unregistered/private REITs, private notes, etc.). One of the more well-known is "Pacific Premier Trust", but there are many competitors for you to compare and consider.

In my experience such IRA custodians charge much higher fees than "ordinary" IRA custodians, and certainly way more than discount brokerages like Vanguard, Fidelity, etc. That is just the nature of the beast. If you're going to do this, you will have to accept the higher fees as part of it. There will likely be ongoing quarterly and/or annual maintenance fees, and pretty much any action you take in the IRA, including buying the notes you're talking about, will require paying a substantial fee for them to handle the paperwork.