Yep, there's some excellent patterns hosted on Jan Andrea's site. I've made a BBO, which is a very easy pattern to make, and it wears very comfortably too. Or there is the Scandi style MT which is a bit more complex but yields very good results.

As for onbus, there is one on the Jan Andrea site, which uses a body and straps made from a place mat and table runner. The straps are similar to that of a BBO. I would be more inclined to use more supportive materials though, especially if you are carrying a toddler. I don't know of any other specific patterns, but you can adapt a preferred mei tai pattern to suit (probably one with an unpadded waist would work better). It's generally preferable to use small sized sling rings (these can be purchased from Sling Rings in the US - it's google-able). The weewuns here do sell sling rings which they import from Sling Rings, but I don't know that I've ever seen them stock the small sized rings.