Like the rest of Prime gear which came out with a Prime warframe, the first option to obtain the Hikou Prime will be buying the Nyx Prime Access, and the Scindo Prime is also included. Depending on which pack you buy, you can also get some unique gear and accessories.
For the ones who can not afford to buy the Prime Access, but don’t want to invest so much time, you can always buy the different parts of the Hikou Prime form other Tenno. Trading has a good side both from the buyer and the seller, and I meet some Tenno specialized on buying or selling parts and never lose in the process. Trading is a real art in Warframe, do not forget that.
And finally, for the most patient Tenno, there is always the option to get the Relics which contain the different parts of the Hikou Prime and open them in the void fissures. In this case you will depend on luck and perseverance. Some of you may not believe me, but I also meet some Tenno with a lot of luck, so many that it seems impossible.