Is it possible that you could "wick" glyphosate onto actively growing Bermuda around your agave? Wear rubber gloves and mop the diluted product onto the Bermuda with a saturated rag, being careful not to touch the agave. Some plants actually have a surface cutin that is waxy and prevents penetration by the product and prevents damage, but I am not sure if agave is one. Get the Bermuda as close as you can without touching it.
hortster