Candy, please read this carefully.
When you offering a product for group buy, this product has to have something special and unique features that can attract a lot of people. This can be a very good price/quality ratio, usefullness, good UI or efficient circuit allowing long run times.
Based on previous experience with group buy, people are interested in high quality brands (Fenix, Sunwayman, Jetbeam, etc.) and their budget priced models. They have very good circiuts, reliable switches, nice build quality and use widely available batteries (AAs or AAAs). Therefore I suggest:
http://www.focalprice.com/LF949B/FENIX_HL21Cree_XPE_R4_4Mode_Warm_White_LED_Head_Light_Black.html
A very nice headlamp. With some discount, it could be priced similiar to Ultrafire 18650 headlamp (UF-H3 if I recall correctly). I think quality difference between those two is obvious. Plus - Fenix comes with diffuser that you can use on other AA lights.
http://www.focalprice.com/LFI54B/JETBeam_BA10_Two_Modes_Cree_R5_EDC_Flashlight_Black.html
Jetbeam BA10. This is simple AA model. Built like a tank, very easy and straightforward UI, good quality and forward click. If priced at ~26-28$ level, this could also be very popular.
http://www.focalprice.com/LF0030B/OLIGHT_Cree_XML_T6_LED_Waterresistent_Ultra_Bright_Flashlight_Black.html
Olight M65. This one is extremely good looking and very versatile light. Very easy UI, diffuser included and nice built quality. If priced under 50$ this could also be a hit.
All these lights use current control in circuit, no PWM, superb built quality and versatility. These are features, that can attract potential buyers. The lights from your first post lack those feature. Apart from low price (I guess so), there's nothing special in them. No "wow" factor at all.