Yes, they exist. I have 2 ways of doing this.
1. is TP-Link TL-MR3420 - see
TL-MR3420 - Welcome to TP-LINK. These cost Rp275,000 at Waroeng Komputer. I use it with a Huawei HSPDA modem - I am not exactly sure which model but maybe an E161 at about Rp250,000. Works fine if your SIM card provider is giving a good 3G service in your area.
2. I have an IDEOS Android phone from Huawei which can act as a wireless hotspot so that nearby laptops etc can use the phones data connection. I think there are a number of Android phones that can do this.
Then, there are single Huawei devices such as E585 that can do it
HUAWEI E585 - Huawei Device Co., Ltd... I have not used one, but have no doubt it would work OK if you have a good 3G signal. Waroeng Komputer has a price of Rp381,000 for these.
Where to get them - you will have no trouble getting the TP-Link and the Huawei USB stick at RTC (Rimo Trade Centre), but last time I asked for a Huawei E585 there I could not find it - maybe now you can. Waroeng Komputer in Jakarta has them all and ships by JNE.