This is an improved variation of my flat mate's recipe. Thanks!
Japanese ingredients are expensive when living abroad, so this kind of knowledge is helpful for you.
These ingredients used are available anywhere, so you can use this okonomiyaki sauce as much as you like, without being sparing.

If you are okay with the smell of the oyster sauce, omit the BBQ sauce and use a 1:1:1 ratio of the other ingredients.
I prefer a ratio of 2:1:1:1.
The oyster sauce is optional. The others are the basic components of okonomiyaki sauce. Recipe by Shasin shokunin