https://civitai.com/models/1223555/riding-for-illustrious

You can ride horses "horseback riding", but now you can ride other things!

Example prompt:

best quality, masterpiece, amazing quality, very aesthetic, absurdres, 1girl, giddyup, horse, blonde, long hair, blue eyes, (large breasts, pink lips:0.75), cowboy hat, looking at viewer, outdoors, trees