Rakshit
Both half fare (travel)cards are fully equivalent regarding what you can purchase with them.
Therefore the discounted saver day pass is also available with the Swiss Half Fare Card.
Note that the validity period of the half fare card related to the travel dates, NOT to the ticket purchase dates. So you can already buy saver day passes without already having the card, this is not checked during the purchase process. Simply tick ‘half fare’ as discount option in your passenger details in order to get the correct discounted prices.