Couple things:
1. You should add your location to your profile. This will enable us to tailor our advice specific to you, which will result in an all around better situation for you.
2. You should post a thread in the Welcome section introducing yourself. Tell us a little about you, what you like, your experiences with lasers, etc. Say whatever you want. That is there to give us a first impression of you
3. Take a look on the Buy/Sell/Trade section of this forum. I was wary when I first joined of buying things online, but this is a great community full of people ready to run off those who would rip you off or scam you. I would say your chances of getting a quality laser are much higher on our B/S/T section than on any of the CHEAP chinese sites.
4. When you say you want a 100mW blue, do you know what wavelength you want? This will have a large effect on the pricing and availability of what you desire.
4a. A 100mW 405nm Laser(Deep Royal Purple) will be highly available at comparatively low cost.
4b. A 100mW 445nm Laser(Royal Blue) will cost more than the purple lasers but will still be fairly available and affordable. Decide if you want good beam specs or a multimode diode and you could probably get a builder to make you one on this forum.
4c. A 100mW 473nm or 488nm will be very expensive, not very available, and will not be as hardy as others due to the way they are made. (For more info, google DPSS diode lasers).
5. INVEST in a pair of Safety Glasses. You are here because you like lasers. Seeing them is almost all the fun. If I was blind, I probably wouldn't give a Rat's A$$ about lasers. Lasers over 5mW have the capability to do permanent eye damage, and you don't want that. See the link in my sig for more info.
Welcome to the forum! You will love it! If you have any questions feel free to PM me. If I don't know I am sure I could find out.
Peace,
Isaac
