There are a million off-the-shelf leave in conditioners. Some contain oil and that's what you want to avoid. Read the labels. There are some that don't 'weigh' the hair down. Also, with summer coming up it's a good idea to look for one that contains UV block to protect against fading. I like Dove products. They have a leave in conditioner called 'Leave in Replenishing Mist' but there are many others that are good too.
Regards,
John