I deal with this problem every time. I have some 'default' repertoire and when preparing against concrete opponent, I find that it is highly probable we will reach some concrete well known position and I want be the one to come with system he can't expect me to play. Ok I can use book, engine, games to create interesting system myself, but it takes soooo much time. People already made thousands of preparations like this, coming with a sharp forcing idea hard to refute over the board, playing new move with completely different approach compared to main lines... Is there somewhere something like market of these ideas? Just pgn with 20 lines, for example. Or text. Anything that is good for titled players, computer checked lines, dangerous surprises for one game etc.
The SOS ("Secrets of Opening Surprises") books and articles (in New in Chess magazine) can be good references. Once in the USATW I was paired up against a 2450 rated player. I found references with a quick online search that he played the Caro-Khan. I walked in the bookstore and looked in an SOS book and found a line Kasparov used in blitz a lot. After 10 minutes of preparation I was armed to get my well booked opponent out of his element and I won my best game of the tournament. I've done such things with the Chess Informants a lot including preparation against Yermolinsky in the US Open. I would say Chess Informant is best if you have the time and money.
i don't know you want a opening repertoire for positional or attacking one. I use to play mainly positional repertoire but for some blitz chooses attacking one. I followed some lectures of yassar serwain's from saint luis club , it is available in youtube . I also follow a pdf of gufeld's repertoire Repertoire of Gufeld and another man
And also following some advice from GM Arthur Yusupov . But at last I must say that if you do not rely on your repertoire then you cannot become a good player , and if you do not make a hard work on your openings then you cannot make a solid typical opening (most of the player don't like this type of opening which has been analysed , like with 48 moves or more!! ) like Lev poluguasky (Pronouncing wrong?!) , His openings homework was great , every player was scared to play with him , he is mainly known for his hardwork on openings (his favorite opening was sicilian najdorf , and he invented the opening Sicilian Najdorf Poluguasky variation , which is sharp like axe ) , if you make a hardwork on your opening you can be one like him . And at one stage he said by this hard work attitude he can prepare any master player into world champion.