Go with Dulux Egyptian Cotton. At ΔE 0.7 from Balboa Mist it's essentially imperceptible — anything under 1 means the average eye can't tell them apart on the wall. Egyptian Cotton sits at LRV 64, a touch above Balboa Mist, so it reads as that same soft, warm greige with the faintest violet undertone that makes Balboa Mist so well-loved.
If you can't get Egyptian Cotton or you fancy a comparison, Dulux Timeless is your runner-up at ΔE 1.3, LRV 61.7. Still a very close match (anything under 2.5 is what we'd call very close), just a hair deeper and slightly less of that pinky warmth. In a north-facing room Timeless might actually be the safer call — it holds its colour a little better when the light goes cool and grey, whereas Balboa Mist and Egyptian Cotton can drift towards mauve in flat northern light.
The "but what about" here is sheen and base. Balboa Mist is a Benjamin Moore colour, and BM's paint has a particular soft, chalky depth that Dulux won't replicate exactly even at ΔE 0.7 — the pigment match is bang on, but the film and the way it scatters light differ slightly between brands. So if you're touching up an existing BM wall rather than starting fresh, a Dulux match will be close but not invisible across a whole wall. For a full repaint it's a non-issue.
Practical advice: order a sample pot of Egyptian Cotton and live with it on a couple of walls for a day or two before you commit a whole tin. Greiges like this are chameleons — they shift with your flooring, your skirting and the time of day. Paint a patch near the window and one in the darkest corner. If it stays warm and clean in both, you're sorted.