The cheapest option is to buy an old oil-wheel projector that you would find in discos and nightclubs during the 70’s & 80’s.
I used to buy them second hand "for this very purpose" from Victor Morris on Argyle Street Glasgow for about £40-£80 each.
All I did was cut the company logo or whatever in reverse in black vinyl and apply it to the glass disk that rotates in front of the projected light. Other than a bracket to hold it, job done!
The attached image is a NEW version of an old oil wheel projector but far too pricey for what they are.
your better buying second hand from an old disco lighting hire company or similar.
Gobo projectors are overkill for what you are looking for. do not get me wrong, they are much better and far more powerful so you can project much further and sharper. again, for what you want I would go for the old oil wheel projector.