@nicolasdupon
I don't know if this will get you out of trouble, but there is an older small Atlantic Basemap Version 2 with some basic WW major roads. It's only 6762496 bytes (6.44MiB) and is non-DEM but DEM data uses a lot of space so maybe your original Basemap doesn't have it and i don't recall it being available on an etrex10 basic B&W screen anyway. Maybe someone has the original basemap for you and will post it but in the mean time here's ATL_V2:
Spoiler:
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