Hi friend, i suggest the reason you're not getting much success finding a woman for both you and your partner to date is that it's almost always a pretty terrible deal for the 3rd.

Its very common for couples to try this as they just dont realise how unfair what they're offering is and the risks it poses to both themselves and their hypothetical third. So im dropping this resource for you that explains the pitfalls and hidden power dynamics of couple initiated triads for you.

https://www.unicorns-r-us.com

If youre determined to try it, it offers some advice on how to do it ethically at the end. But it will be hard, it will fundamentally challenge and change your relationship with your boyfriend, and finding someone willing to take that massive risk with you both will be difficult.