I have/had the same question recently. Due to the odd nature of the On One Whippet frame I couldn’t just stick a simple jump stop on which was most annoying. Anyway I didn’t have enough spare cash to buy any of the recommended options so I have nothing other than a bash guard, so far I have done 200 miles most of whch are on the SDW and have had one dropped chain.
I will have to cover this with the statement that I am not very clued up on this biking lark other than I try to get out as often as I can so i don’t have extensive experience of riding with a single ring up front but 200 miles and one drop gets me wondering if the guide is as important as some would make out?