It does seem that injectable Tylan is hard to find. Here is a link for oral Tylan that is put into the water. The water should be added to the water, not the other way around or it won’t mix well. Dosage is 1 tsp per gallon for 5 days.
https://www.jedds.com/shop/tylan-soluble-100-g/
https://www.jedds.com/shop/tylan-soluble-100-g/