I was able to get my hands on an original halo bulb kit. There are 8 bulbs in total. The Subaru part number is 85091AE000.
6 of the bulbs are the larger 14V3WL made by Toshiba. These have a blue base with a yellow paint mark.
The other 2 are the smaller Type 80 bulb, also made by Toshiba. These have a black base with a blue paint mark.
Toshibas part number for the larger bare bulb is A7824. It is a 6.5mm-T2 W2.2x5.2D wedge rated for 214mA @14V, with 15 lumens output and a 5000 hour life. Reference "61 431"
Toshibas part number for the smaller bare bulb is A7429. It is a 5.0mm-T1.5 W2x4.6D wedge rated for 140mA @14V, with 8 lumens output and a 5000 hour life. Reference "80"
The type 80 bulb is physically the same as a Type 74, except that its operational life is 5 times longer. (5000hrs vs 1000hrs)
I am trying to find a US source for these bulbs, and I will update this once I find them.