My (42M) wife (F41) of 18 years has numerous health and mental conditions that prevent most sexual activities. Recently she told me she would be ok if I found a sexual partner to meet my sexual needs. I'm not sure what to do.

So we're a fairly classic couple story where we have very different libidos. Mines been high and hers was a bit lower until about 10 years ago. Over the past 10 years she's been diagnosed with multiple health conditions. I don't want to list them all, but needless to say it's deeply effects her standard of living and puts me in the role of a caregiver.
I love my wife, when we first got married none of these health conditions were present. But if they had been, I still would have married my wife.
My real only concern has always been the reduction in our sex lives. Over the past 2 years it's been really noticable, with sex occurring once maybe every couple months, with some gaps as long as 6 months.
I know my needs aren't really being met, and I struggle greatly to even accept that my sexual needs are important in the face of what she goes through everyday. To be clear, she's a hero in my eyes she faces all her struggles with strength. Even when she falters and has a bad day she picks herself back up and faces the next day. I feel so guilty feeling bad about wanting sex, when clearly she's struggling with so much more.
She mentioned about a week ago that she knows I stay up late so I can masterbate after she goes to bed, and the she knows that I want more sex. She told me she feels guilty she can't provide the level sexual activity I desire. And that after taking care of her for so many years I deserve to have these needs met. She ended by saying that I could try to find a sexual partner to fill my needs, but the huge caveat is she doesn't want to know anything about it.
This isn't completely out of nowhere, many years ago, before her illness, we were a pretty experimental couple for sex. While the drive was lower for her she was still adventurous. We had a few group sex activities, and she struggled with some feelings of jealously. We worked through them and eventually had a few positive encounters with multiple people.
She said she knows that after everything we've already gone through that I'm loyal to her, but she's willing to give me the ability to find a sexual partner for meeting my needs. I don't know how I feel about it. Especially given the jealousy situation from many years ago. I'm really confused, I have no ethical problem with open relationships, but I am worried this will backfire on me. I'm also worried I simply won't be able to find a partner since I have no idea how to even look after being with someone for nearly 20 years.
Truthfully I'd love to be able to have sex with someone, and I don't link sex with love and romance. But how do I even do this if was going to? What does Dating.mobi think?
TL;DR: my wife has a ton of health conditions that means she can't do much sexually. She recently said I can find a partner to have my sexual needs met. I don't know what to do cause I'm definitely interested but worried about consequences.
edit: the reason she doesn't want to know is more due to her lack of self-confidence after years of health issues than jealousy. I just mentioned the jealousy since it had happened in the past.


Source.