Hey there, generally most yellow crystals can be used for solar plexus for this chakra is associated with color yellow. Apart from Citnine, i found Yellow Calcite and Tigers' Eye is quite suitable. For sacral (red/orange) orange Carnelian is really good. Also having issues with sacral chakra (Dan Tien) my self i really do recommend Falun Gong (Dafa) meditation. Its a really good (and easy to learn) energy freeing and healing meditation technique and it is free to read about and watch on the website (which im not allowed to post yet so just google it) I found after an effective meditation practice, my interaction with crystals increase exponentially for a period of time. So u could giv that a go as well if you are interested.