I have seen many diy fails even with products pros use to make beautiful repairs.
I would suggest a bathtub chip and repair company.
They can repair the chip and buff out the tub so it is invisible.
There are porcelain repair products out there that can be done on the side wall but these require additional tools a dual action sander is one of those tools I prefer the 2 part kits and if you can get under the tub and find the color Code you can order the right pigment This is where the pros shine they have a color chart mix and adjust the color apply with a putty knife cure with UV light then buff it out , the home kits take much more time and since we don’t do it often it usually is obvious where the repair is.
It can be done if not an epoxy 2 part it will take multiple coats and still have to sand the advantage to that method is you can tell on the first coat if the product matches and make adjustments but that method usually leaves a shadow
So it can be done but more looking online and don’t think 10$ kit will do it look in the 30-50$ range for a kit that will do they job Match color and last.