I would order exactly the original type. Then important specs are correct. Transistor type doesn't effect that much on heat generation in this design. Low Rds(on) is better in switchers = lower power loss. Overall regulator structure mostly defines efficiency.

That would be wise, but I was unable to find either the 45N03 or the the nec k2941 from tme, where I usually source caps and such stuff...

The information contained in this video https://www.youtube.com/watch?v=9wuyPZjjR9k can help you find a replacement.