The 13 to 34 megarange used to have a 15 tooth second sprocket, so you could have used one of those and ignored the 13 one, but sadly they are discontinued and I can't find any leftover stock.
I'm assuming yours is the one with a 16 tooth second sprocket and you find that too low to use instead.
If you don't mind buying from the USA,
Harris Cyclery (scroll down) have the alternative one, 14 to 34 with a 15 tooth second sprocket, so you could use that and ignore the 14 tooth. Although I haven't found one, there may be a supplier this side of the pond with one.
The problem with changing the chainwheel instead is that it may not be very standard, appearing to be
slightly dished to suit the chainguard. A standard chainwheel may leave the chain misaligned too far out and not suiting the chainguard, but I can't be sure from photos.
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