2 things come to mind:
1st - is he tired? Can you take him for an extra walk to make sure to wear him out so he sleeps through the night? Also, can you feed him later in the day so that he is not waking up hungry? Mine eat twice a day and the earlier I feed them their dinner the earlier they are up wanting breakfast, sometimes 2 hours before we normally get up.
2nd - how much water is he drinking and when? I wonder if he is drinking too much or drinking too much close to bedtime.
The bottom line is that he shouldn't be having accidents unless he is kept in there too long and he really does have to go, so it might just take some adjusting of his schedule. Like when his dinner is, when you take up water, when you last take him outside... I find that one extra trip outside before bed gives me an extra 30-60 minutes in the morning
The good news is that at 10 months you are almost there!!!