any substitute from auto repair shop?

I used ATF fluid in a pinch before...

how about motor oll that i used inside engine? the filter oil is to prevent/stick the dust, right?

If they also carry products targeted at motorcycles chances are they also have some sort of air filter oil, though it's usually a lot thicker than what's commonly used in the on road sector, some of the off road guys use it, mainly because you can buy a can of it and never again worry about it running out. Chainsaw bar oil also has very similar properties (very sticky).
2 stroke oil should also be usable if you're looking for something that's a little thinner viscosity.

2 stroke oil means the motor oil for 2 stroke motorbike? i am no expert in bike

Correct, the stuff you use for pre-mix.

Basically any oil will work better than no oil. Even some RTR brands advise to use afterrun oil which I also o for many years.

A good and very stickey oil is from Putoline called Action Fluid and is special for foam filters. It also comes in a handy spray can.
https://www.putoline.com/en/catalogu...on-fluid/1659/

I use Team Associated air filter oil. Soaks in easily, then thickens to be incredibly sticky, so it won't get sucked into the engine and leave the filter dry. Also it doesn't degrade foam sponges like some air filter oils I've seen. But as roelof said, in an emergency any oil is better than none.

I've previously used after run oil also when racing offroad nitro buggy way back when.

Ive followed tips from Jeff Hamon and oil from inside and let it soak to the outside also

Airflow through the filter will draw the oil to the inside of the filter over time. Soaking the filter from the inside may produce a more visually-satisfying oil saturation, but it won't produce better filtering, since the air has already been cleaned by the time it reaches the innermost part of the filter. It is likely that any oil applied to the inside of the filter will get sucked into the engine the first time you rev it to full-throttle -- especially if the air filter is very close to the carb inlet and is getting damp with fuel splashing out of the carb at idle.

Motocross air filter oil is the proper stuff. Any brand will do!

I've used Notoil oil filter for motorcross bikes but it was a little to thick. It caused tune issues. I only use the Novarossi airfilter oil. while its still around????

It is not hard to use too much in the case of Motocross filter oil, especially because the on road foam is black so you can't guess the level of saturation very well. The foam being permanently attached to the rubber piece doesn't help much either as it makes removing excess oil more difficult.
It's perfectly fine to use once you get the hang of it though.

True, you can get it wrong - coming from off-road and white filters, this was a struggle initially. But it's really simple, just put large drops on a few places and gently massage it, not to rip the foam. With a strongly coloured oil (mine is very deep blue) you will easily see if there's any blank spots left. Then wipe it off (very very very important) and leave it for a while. I'd never oil a filter at the track and put it on, I prepare them weeks in advance as a part of regular maintenance.

BTW for me it's even worse with Novarossi oil (I have it), because it's without color and thicker than my Twin Air motorcross air filter oil (still very tacky)