@sun, good afternoon A, hmm that has been a problem this year, a lot of nurseries have been selling out due to Covid and more people staying at home working on the garden. Hopefully the German nursery has the trees you want. As you have used them before you at least know the quality of their maples. 'No shocks'. 9cm pots are OK, but I would want them at the beginning of the year rather than the latter, especially in your gardening zone. They are great fun though seeing them grow and you feel that you have had a real hand in their development. Let us all know how you get on?