Furikake is easy to make at home. My aunt would make it all the time after making dashi. I would suggest to use mushroom powder instead of katsuobushi (The fish) for that umami.

Admittedly I have never done this with furikake, but I do use mushroom as substitute for stocks in hot pots, soups, etc for vegan/vegetarian friends when they come over.

Here is a link to shiitake mushroom powder. This company also makes others. I will say it is also easy to make your own at home with dried mushrooms and a spice grinder. Best of luck. mushroom powder amazon