I have just found out that this is possible via the company Sertronics. Unfortunately, the cost of a drinking spout (incl. VAT) without shipping is already 10.78.- and shipping costs another 14.59.-.
Apparently the spare parts have to be imported at great expense and the prices for the spare parts are set by the manufacturer.

I think it's a shame that the whole product is cheaper than a spare part. This only encourages the throwaway society.

Nevertheless, it would be possible. However, I have noticed that the MAM drinking spouts also fit into the lid.

Unfortunately, the drinking spout is not available separately.