Mickey Thompson SRs are an option at 15". They have a modern "flame" tread pattern. According to the company they are designed for hot rods (not that it matters if you like the tread). The tread compound is softer than the STs or Cooper Cobras.
mickey thompson sportsman s/r tires
Mickey Thompson Sportsman STs are also available at 15". They have a more traditional tread pattern.
https://www.performanceplustire.com/tires-for-sale/mickey-thompson-tire/sportsman-s-t-radial-tire/
Cooper Cobras are the same compound and tread pattern as Mickey Thompson STs. According to the techs I spoke to at Cooper and Mickey Thompson, the MT STs and Cooper Cobras are the same compound and tire, but have different patterns on the sidewalls.
https://www.tirerack.com/tires/BigPic.jsp?gclid=CjwKCAiAtorUBRBnEiwAfcp_Y87TqoLge YaDWKWhhN8stJzD0ikD551hFCX4gRztd-49XP95hU9vKRoCqmoQAvD_BwE&tireMake=Cooper&tireMode l=Cobra+Radial+G%2FT&partnum=17TR5CRGTRWL&GCID=C13 674x012-tire&KEYWORD=tires.jsp_Cooper_Cobra_Radial_G%2FT_T ire&code=yes&src=17540115&ci_sku=17TR5CRGTRWL&ci_s ku=17TR5CRGTRWL&ci_src=17588969&s_kwcid=AL%213756% 213%2172322431853%21%21%21g%21175653683053%21&ef_i d=V38gbwAAADwu3Hph%3A20180213141140%3As&sidewall=R aised+White+Letters
The Coopers are about 30% less expensive than Mickey Thompsons, and in my area are in stock at Discount Tire, but it takes a few weeks to get the MTs.
As an aside, Cooper Tire owns the Avon and Mickey Thompson brands.