Any good alternative to Mr Surfacer 500?

I am giving up on finding Mr Surfacer 500 anywhere but need to neatly fill narrow seams between wings and fuselage on my Monogram AT-6. What makes a reasonable replacement for Mr Surfacer 500?

Vivian

Tamiya’s Liquid Surface Primer in the 40ml jars is very similar to Mr Surfacer, though it’s finer than MS 500. Tamiya’s product also comes in white, and is soluble in denatured alcohol (as well as the recommended lacquer thinner) so it’s a little more user-friendly.