If you can't buy those lights then I would take them outside whenever you have the time, live steve said, until you have the money. Where do you live ? Do you have a pet store near you ? Because buying locally is often cheaper than ordering online (no delivery cost).
I did find a 75 w bulb, but it doesn't seem to have a good review on Amazon. Never heard of this brand before, anyone ?
https://www.amazon.com/ABURA-spectrum-R ... B01M28F30JEDIT: I would also think of long term. Maybe taking your time to buy another lamp for 15 w - 25 w would be cheaper for you in the long run because the lightbulb I shared costs a lot IMO.