I've got a Moby and an Ergo but it was 90 degrees here today and both seem pretty hot (Ergo with the infant insert). I'm also poor so I don't really want to spend more than $$40-$50 tops! I sew so I could make my own.
Your cheapest options and easy to DIY would be either a cotton gauze wrap or a linen ring sling. You can do a linen wrap but I personally find them more difficult to work with and that won't end up being particularly cheap. Osnaburg is another
Re: Best Baby Carry for Summer?
Breastfeeding Counselor with Breastfeeding USA
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