You are less likely to break your fingers doing no-Gi anyway as there is much less likelihood of catching fingers awkwardly while you are rolling. You could try taping your fingers although this will only protect you to a certain degree and will hinder your finger movement range. The taping will help if you have a pre-existing problem with finger(s). Other than that you could try using MMA gloves but that will likely give you another area to hurt yourself. Short of it is you should not break your fingers in No-Gi BJJ.