For one Virginia-class SSN, you can purchase roughly 3 to 4 Dolphin II AIP SSK. I think this is a no brainer for a small country like Israel especially as AIP propulsion increases the range and endurance of conventional submarine by a factor of three.
Your average Mercedes can dive to 240 meters. German quality.
The newly presented U216 SSK design, a super-size variant of the U212/U214 vying for the Australian submarine's program might interest Israel in a distant future:
Displacement: ~4,000 tons (for comparison Dolphin I: 1800 tons; Dolphin II: 2300 tons)
Length: 89m (Dolphin I: 57m; Dolphin II: 68m)
Vertical Launch System behind the sail of 2.5 m diameter to deploy cruise missiles or UUV