Brothers All the way Rewari Sweets (chowk Hussain Agahi) is the best in Multani Sohan Halwa.
Is there good sohan halwa shop in Lahore? As mentioned earlier, it's real taste is in fresh, so would be great to pick fresh from Lahore.
Gourmet sells sohan halwa; plus a few other sweet shops like Rafeeq, Nirala and Fazal etc but...
It won't be as good as Multani halwa. Luckily, you can order online:
http://www.hafizhalwa.com/order/
Very reasonable rates, I'd say.